The present invention relates to an apparatus for dyeing and bleaching yarns and textile products in general, particularly for stockings and pantyhose made of nylon or other materials.
Machines for dyeing or bleaching textile products in general are known; such machines are generally constituted by a tank intended to contain the treatment liquid and in which the products to be treated are placed. Such machines are divided into two categories: machines for treating products which can be crumpled and arranged in a disorderly fashion, and machines for treating products which need to be left carefully folded or laid out.
In machines for treating crumpled products, said products are thrown into cloths or sacks which are permeable to the treatment liquid and said cloths or sacks are inserted in the tank in a more or less orderly manner, filling in the best possible manner all the available spaces so that preferential channels for the flow of liquid are not defined at any point in the volume of products, which would lead to a non-uniform dyeing, usually termed streaking. The tank is filled with water, and the chemical treatment products are added in the various steps of the process; said water, properly termed bath, is moved so as to flow through the products alternately upwards from below and downwards from above.
In machines for treating carefully folded or laid out products, said products, either placed in cloths or sacks or unprotected, are loaded in stackable drawers or containers which are placed in a parallelepipedal tank, and the dyeing bath flows through them substantially as already described for machines for treating crumpled products.
The treatment using drawers, differently from the treatment of crumpled products, maintains the products substantially as they appear when they are loaded, i.e. without wrinkles and well-pressed.
Both treatment methods have been used for a long time, in particularly in sock- and stocking-making factories, despite not being economical mostly due to the high ratio between the weight of the bath and the weight of the products to be treated.
Devices with a cylindrical tank are also known and used for dyeing treatments for textile fibers; said machines are used and conceived to circulate the bath through the textile fibers with a radial circulation. Said devices, in their use for dyeing stockings and pantyhose made of nylon or other materials, force the circulation of the bath in only one direction, since during the dyeing treatment the material bathed in warm water loses volume, facilitating the formation of preferential paths, with the disadvantage of a non-uniform dyeing.
In order to obviate this disadvantage, an apparatus with a cylindrical tank has been provided in which the bath is subjected to an alternated vertical circulation, as in the previously described machines.
Said apparatus, described in the patent application No. 22.353 B/83 filed on July 13, 1983, allows a considerable reduction in power consumption, since it can operate with considerably reduced amounts of bath with respect to the previous machines, with a consequent saving in steam for heating the bath, in water, in chemical treatment products and in electric power.
Said apparatus comprises a cylindrical tank with a vertical axis and a cylindrical perforated container on which the products to be treated are placed, conveniently placed in sacs or cloths permeable to the treatment liquid.
The treatment bath circulates vertically inside the tank, passing alternately through the container of the products in one direction and along an annular space outside the container in the opposite direction.
Said apparatus, though it allows a considerable energy saving with respect to prior devices, can be used only for the dyeing of crumpled products, due to the structure of the product container.